In this study, researchers will learn more about the effects of diroximel fumarate (DRF), also known as VUMERITY®, when taken during pregnancy in people with multiple sclerosis, also known as MS. In MS, the immune system attacks the nerves in the brain and spinal cord. The affected areas are called lesions. The damage makes it difficult for the brain and spinal cord to function and send messages throughout the body. MS can be a progressive disease, which means it may get worse over time. In relapsing forms of MS (RMS), new symptoms may happen, and existing symptoms may get better or worse over time. DRF is an approved drug that is used to treat people with RMS. This is known as an observational study, which collects health information about study participants without changing their medical care. The main goal of this study is to collect birth and health information from 3 groups of participants and their babies. These groups are: * Those who took DRF during their pregnancy * Those who took other drugs for RMS during their pregnancy, but not DRF * Those who did not take any drugs for RMS during their pregnancy The main question researchers want to learn about in this study is: • How many participants' babies were born with major congenital malformations (MCMs)? MCMs are problems with how a baby's body forms before birth. Researchers will also learn more about: * Loss of the baby before 20 weeks of pregnancy * Loss of the baby at and after 20 weeks of pregnancy * How many babies are born early (at or before 37 weeks) * How many babies are small for their age while in the participant's uterus * How many babies are born with any sign of life This study will be done as follows: * Participants with RMS can join this study if they become pregnant from 29th October 2019 to 31st July 2030. Information will start being collected when the participant decides to join the study. * The participants' medical records will be reviewed 2 times during the study - once when the study is halfway done, and one at the end of the study. * Each participant will be in the study until the end of their pregnancy. Each baby will be in the study for up to 1 year after birth. * The study is planned to end by 30th April 2031.